1. Field of the Invention
The present invention relates to a stereoscopic display achieving stereoscopic vision by a lenticular system.
2. Description of the Related Art
In related art, one of stereoscopic display systems which are allowed to achieve stereoscopic vision with naked eyes without wearing special glasses is called a lenticular system using a lenticular lens. As illustrated in FIG. 12, the lenticular lens is a cylindrical lens array 302 in which a large number of semicolumnar lenses called cylindrical lenses 303 having refractive power only in a one-dimensional direction are arranged in a one-dimensional direction. The lenticular system has a configuration in which the cylindrical lens array 302 is arranged to face a display surface of a display panel 301 configured of a two-dimensional display. Each of the cylindrical lenses 303 arranged so as to extend in a longitudinal direction of a display surface of the display panel 301 and to have refractive power in a lateral direction. A plurality of display pixels are regularly two-dimensionally arranged on the display surface of the display panel 301. In the lenticular system, two or more pixels are arranged on a back surface of one cylindrical lens 303, and light rays from the pixels are emitted in different horizontal directions by the refractive power of the lens so as to satisfy binocular parallax, thereby stereoscopic vision is achievable. In the case where the number of pixels arranged on the back surface of the lens is 3 or more, motion parallax is obtained, and when the number of pixels is increased, light rays emitted from a real three-dimensional object are allowed to be reproduced precisely.
In an example illustrated in FIG. 12, two adjacent pixel lines 301R and 301L on the display surface of the display panel 301 are allocated to each cylindrical lens 303, and a right parallax image is displayed on one pixel line 301R, and a left parallax image is displayed on the other pixel line 301L. The displayed parallax images are distributed to right and left optical paths 402 and 403, respectively, by each cylindrical lens 303. Thereby, when a viewer 400 sees a stereoscopic display from a predetermined position in a predetermined direction, the right and left parallax images appropriately reach right and left eyes 401R and 401L of the viewer 400, respectively, thereby the viewer 400 perceives a stereoscopic image.
Likewise, in the case of a multi-view system, a plurality of parallax images taken in positions and directions corresponding to three or more viewpoints are equally divided in a lens pitch in a transverse direction of the cylindrical lens 303, and then allocated to be displayed. Thereby, three or more parallax images are emitted by the cylindrical lens array 302 in successive different angular ranges to form an image. In this case, a plurality of different parallax images are perceived by changing the position and the direction of the viewpoint of the viewer 400. The more the number of different parallax images corresponding to viewpoints is increased, the more realistic three-dimensional appearance is obtainable.
As the cylindrical lens array 302, for example, a resin-molded lens array of which the shape and the lens effect are fixed is applicable, but in this case, the lens effect is fixed, so the display is for three-dimensional display only. Moreover, as the cylindrical lens array 302, for example, a variable lens array configured of liquid crystal lenses is applicable. The variable lens array configured of liquid crystal lenses is electrically switchable between a state where the lens effect is produced and a state where the lens effect is not produced, so switching between two display modes, that is, a two-dimensional display mode and a three-dimensional display mode is allowed to be performed by a combination of the variable lens array and a two-dimensional display. More specifically, in the two-dimensional display mode, the lens array is turned into the state where the lens effect is not produced (a state where the lens array does not have refractive power), and display image light from the two-dimensional display passes through the lens array as it is. In the three-dimensional display mode, the lens array is turned into the state where the lens effect is produced, and the display image light from the two-dimensional display is deflected in a plurality of viewing angle directions so as to achieve stereoscopic vision.
FIGS. 13A, 13B, 14 and 15 illustrate an example of the variable lens array configured of liquid crystal lenses. As illustrated in FIGS. 13A and 13B, the lens array includes a first transparent substrate 101 and a second transparent substrate 102 which are made of, for example, a glass material, and a liquid crystal layer 103 sandwiched between the first substrate 101 and the second substrate 102. The first substrate 101 and the second substrate 102 are arranged to face each other with a distance d in between.
As illustrated in FIGS. 14 and 15, a first transparent electrode 111 configured of a transparent conductive film such as an ITO film is uniformly formed on substantially the whole surface on a side facing the second substrate 102 of the first substrate 101. Moreover, as illustrated in FIGS. 14 and 15, a second transparent electrode 112 configured of a transparent conductive film such as an ITO film is partially formed on a side facing the first substrate 101 of the second substrate 102. As illustrated in FIG. 15, the second transparent electrode 112 has, for example, an electrode width L, and extends in a longitudinal direction. A plurality of the second transparent electrodes 112 are arranged in parallel at intervals corresponding to a lens pitch p when a lens effect is produced. A space between two adjacent second transparent electrodes 112 is an opening with a width A. In addition, in FIG. 15, to describe the arrangement of the second electrodes 112, a state where the variable lens array is turned upside down, that is, the first substrate 101 is placed on an upper side, and the second substrate 102 is placed on a lower side is illustrated.
In addition, an alignment film (not illustrated) is formed between the first transparent electrode 111 and the liquid crystal layer 103. Moreover, an alignment film is formed between the second transparent electrodes 112 and the liquid crystal layer 103 in the same manner. In the liquid crystal layer 103, liquid crystal molecules 104 having refractive index anisotropy are uniformly distributed.
As illustrated in FIG. 13A, in the lens array, in a normal state where an applied voltage is 0 V, the liquid crystal molecules 104 are uniformly aligned in a predetermined direction determined by the alignment films. Therefore, a wavefront 201 of a transmission light ray is a plane wave, and the lens array is turned into a state with no lens effect. On the other hand, in the lens array, as illustrated in FIGS. 14 and 15, the second transparent electrodes 112 are arranged with the openings with the width A in between, so when a predetermined drive voltage is applied in a state illustrated in FIG. 14, an electric field distribution in the liquid crystal layer 103 is biased. More specifically, such an electric field that electric field strength increases according to the drive voltage in a part corresponding to a region where the second transparent electrode 112 is formed, and gradually degreases with decreasing distance to a central part of the opening with the width A is generated. Therefore, as illustrated in FIG. 13B, the alignment of the liquid crystal molecules 104 is changed depending on an electric field strength distribution. Thereby, the wavefront 202 of the transmission light ray is changed so that the lens array is turned into a state where a lens effect is produced by changing a refractive index distribution in the liquid crystal layer 103.